Impact of urban imperviousness on boundary layer meteorology and air chemistry on a regional scale

Field measurement programs in Brazil during the dry season months of August and September in 1979 and 1980 have demonstrated the great importance of the continental tropics in global air chemistry. Especially in the mixed layer, the air composition over land is much different from that over the ocean and the land areas are clearly longe scale sources of many inportant trace gases. During the dry season much biomass, burning takes place especially in the cerrado regions leading to substantial emission of air pollutants, such as CO, NOx, N2O, CH4 and other hydrocarbons. Ozone concentrations are alsoenhanced due to photochemical reactions. Biogenic organic emissions from tropical forests play likewise an important role in the photochemistry of the atmosphere. Carbon monoxide was found to be present in high concentrations in the boundary layer of the tropical forest, but ozone concentrations were much lower than in the cerrado.

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The potential for regional-scale bias in top-down CO<sub>2</sub> flux estimates due to atmospheric transport errors

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-23681-2014 ◽

2014 ◽

Vol 14 (16) ◽

pp. 23681-23709

Author(s):

S. M. Miller ◽

I. Fung ◽

J. Liu ◽

M. N. Hayek ◽

A. E. Andrews

Keyword(s):

Boundary Layer ◽

Atmospheric Transport ◽

Regional Scale ◽

Co2 Flux ◽

Atmospheric Co2 ◽

Co2 Fluxes ◽

Atmospheric Measurements ◽

Meteorological Model ◽

Co2 Transport

Abstract. Estimates of CO2 fluxes that are based on atmospheric data rely upon a meteorological model to simulate atmospheric CO2 transport. These models provide a quantitative link between surface fluxes of CO2 and atmospheric measurements taken downwind. Therefore, any errors in the meteorological model can propagate into atmospheric CO2 transport and ultimately bias the estimated CO2 fluxes. These errors, however, have traditionally been difficult to characterize. To examine the effects of CO2 transport errors on estimated CO2 fluxes, we use a global meteorological model-data assimilation system known as "CAM–LETKF" to quantify two aspects of the transport errors: error variances (standard deviations) and temporal error correlations. Furthermore, we develop two case studies. In the first case study, we examine the extent to which CO2 transport uncertainties can bias CO2 flux estimates. In particular, we use a common flux estimate known as CarbonTracker to discover the minimum hypothetical bias that can be detected above the CO2 transport uncertainties. In the second case study, we then investigate which meteorological conditions may contribute to month-long biases in modeled atmospheric transport. We estimate 6 hourly CO2 transport uncertainties in the model surface layer that range from 0.15 to 9.6 ppm (standard deviation), depending on location, and we estimate an average error decorrelation time of ∼2.3 days at existing CO2 observation sites. As a consequence of these uncertainties, we find that CarbonTracker CO2 fluxes would need to be biased by at least 29%, on average, before that bias were detectable at existing non-marine atmospheric CO2 observation sites. Furthermore, we find that persistent, bias-type errors in atmospheric transport are associated with consistent low net radiation, low energy boundary layer conditions. The meteorological model is not necessarily more uncertain in these conditions. Rather, the extent to which meteorological uncertainties manifest as persistent atmospheric transport biases appears to depend, at least in part, on the energy and stability of the boundary layer. Existing CO2 flux studies may be more likely to estimate inaccurate regional fluxes under those conditions.

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Publications by Professor H. A. Panofsky in Boundary-Layer Meteorology

Boundary Layer Studies and Applications ◽

10.1007/978-94-009-0975-5_2 ◽

1989 ◽

pp. 15-16

Author(s):

R. E. Munn

Keyword(s):

Boundary Layer ◽

Boundary Layer Meteorology

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Simulations of Black Carbon Over Indian Region: Improvements and Implications of Diurnality in Emissions

10.5194/acp-2019-152 ◽

2019 ◽

Author(s):

Gaurav Govardhan ◽

Sreedharan Krishnakumari Satheesh ◽

Krishnaswamy Krishna Moorthy ◽

Ravi Nanjundiah

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

Radiative Forcing ◽

Regional Scale ◽

Early Morning ◽

Temporal Variations ◽

Indian Region ◽

Near Surface ◽

Aerosol Radiative Forcing ◽

Convective Mixing

Abstract. With a view to improving the performance of WRF-Chem over the Indian region in simulating BC (black Carbon) mass concentrations as well as its short-term variations, especially on diurnal scale, a region-specific diurnal variation scheme has been introduced in the model emissios and the performance of the modified simulations has been evaluated against high-resolution measurements carried out over 8 ARFI (Aerosol Radiative Forcing over India) network observatories spread across India for distinct seasons; pre-monsoon (represented by May), post-monsoon (represented by October) and winter (represented by December). In addition to an overall improvement in the simulated concentrations and their temporal variations, it has also been found that the effects of prescribing diurnally varying emissions on the simulated near-surface concentrations largely depend on the boundary layer turbulence. The effects are perceived fast (within about 2–3 hours) during the evening–early morning hours when the atmospheric boundary layer is shallow and convective mixing is weak, while they are delayed, taking as much as about 5–6 hours, during periods when the boundary layer is deep and convective mixing is strong. This information would also serve as an important input for agencies concerned with urban planning and pollution mitigation. Despite these improvements in the near-surface concentrations, the simulated columnar aerosol optical depth (AOD) still remains largely underestimated vis-a-vis the satellite retrieved products. These modifications will serve as a guideline for further model-improvement initiatives at regional scale.

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Simulations of black carbon over the Indian region: improvements and implications of diurnality in emissions

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-8229-2019 ◽

2019 ◽

Vol 19 (12) ◽

pp. 8229-8241 ◽

Cited By ~ 3

Author(s):

Gaurav Govardhan ◽

Sreedharan Krishnakumari Satheesh ◽

Krishnaswamy Krishna Moorthy ◽

Ravi Nanjundiah

Keyword(s):

Boundary Layer ◽

Black Carbon ◽

Radiative Forcing ◽

Regional Scale ◽

Early Morning ◽

Temporal Variations ◽

Indian Region ◽

Near Surface ◽

Aerosol Radiative Forcing ◽

Convective Mixing

Abstract. With a view to improving the performance of WRF-Chem over the Indian region in simulating BC (black carbon) mass concentrations as well as its short-term variations, especially on a diurnal scale, a region-specific diurnal variation scheme has been introduced in the model emissions and the performance of the modified simulations has been evaluated against high-resolution measurements carried out over eight ARFI (Aerosol Radiative Forcing over India) network observatories spread across India for distinct seasons: pre-monsoon (represented by May), post-monsoon (represented by October) and winter (represented by December). In addition to an overall improvement in the simulated concentrations and their temporal variations, we have also found that the effects of prescribing diurnally varying emissions on the simulated near-surface concentrations largely depend on the boundary layer turbulence. The effects are perceived quickly (within about 2–3 h) during the evening–early morning hours when the atmospheric boundary layer is shallow and convective mixing is weak, while they are delayed, taking as much as about 5–6 h, during periods when the boundary layer is deep and convective mixing is strong. This information would also serve as an important input for agencies concerned with urban planning and pollution mitigation. Despite these improvements in the near-surface concentrations, the simulated columnar aerosol optical depth (AOD) still remains largely underestimated vis-à-vis the satellite-retrieved products. These modifications will serve as a guideline for further model-improvement initiatives at a regional scale.

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ASIRI: An Ocean–Atmosphere Initiative for Bay of Bengal

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-14-00197.1 ◽

2016 ◽

Vol 97 (10) ◽

pp. 1859-1884 ◽

Cited By ~ 44

Author(s):

Hemantha W. Wijesekera ◽

Emily Shroyer ◽

Amit Tandon ◽

M. Ravichandran ◽

Debasis Sengupta ◽

...

Keyword(s):

Boundary Layer ◽

High Resolution ◽

Indian Ocean ◽

Bay Of Bengal ◽

Regional Scale ◽

Ocean Dynamics ◽

Coastal Current ◽

Northeast Monsoon ◽

Low Salinity ◽

Salinity Water

Abstract Air–Sea Interactions in the Northern Indian Ocean (ASIRI) is an international research effort (2013–17) aimed at understanding and quantifying coupled atmosphere–ocean dynamics of the Bay of Bengal (BoB) with relevance to Indian Ocean monsoons. Working collaboratively, more than 20 research institutions are acquiring field observations coupled with operational and high-resolution models to address scientific issues that have stymied the monsoon predictability. ASIRI combines new and mature observational technologies to resolve submesoscale to regional-scale currents and hydrophysical fields. These data reveal BoB’s sharp frontal features, submesoscale variability, low-salinity lenses and filaments, and shallow mixed layers, with relatively weak turbulent mixing. Observed physical features include energetic high-frequency internal waves in the southern BoB, energetic mesoscale and submesoscale features including an intrathermocline eddy in the central BoB, and a high-resolution view of the exchange along the periphery of Sri Lanka, which includes the 100-km-wide East India Coastal Current (EICC) carrying low-salinity water out of the BoB and an adjacent, broad northward flow (∼300 km wide) that carries high-salinity water into BoB during the northeast monsoon. Atmospheric boundary layer (ABL) observations during the decaying phase of the Madden–Julian oscillation (MJO) permit the study of multiscale atmospheric processes associated with non-MJO phenomena and their impacts on the marine boundary layer. Underway analyses that integrate observations and numerical simulations shed light on how air–sea interactions control the ABL and upper-ocean processes.

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